Control system for catalytic reactors



June 3, 1952 N. F. PRESCOTT CONTROL SYSTEM FOR CATALYTIC REACTORS 4 Sheets-Shea?, l

Filed June 20, 1947 June 3, 1952 N. F. PREsco'l-T CONTROL SYSTEM FOR CATALYTIC REACTORS 4 Sheets-S'neefrl 2 Filed June 20, 194'? nven tor Norman jf? Prescat June 3, 1952 N. F. PRI-:SCOTT CONTROL SYSTEM FOR CATALYTIC REACTORS 4 Sheets-Sheet 3 Filed June 20, 1947 Inventor; Norman Z''resco tt A tfys.

JUIN? 3, 1952 N. E. PREsAcoTT 2,599,197

CONTROL SYSTEM FOR CA\TALYTIC REACTORS Filed June 2o, 1947 '4 sheets-sheet 4 fg a.

Ila/antan Norman Ffres'att Patented June 3, 1952 UNI TED fIiCE v essaier- .REACTORS ,Norman ,-F.- :.Pizesmitti enhan, vlS/Iaissi;rossignol* 'to ,Atwood ik Mor-:lll "n.; :Salemi nf'Mass,-, ,fa corpo- -rationmiMassachusetts Ami' lieation iune, 1947i"Serialivialts This invention :relates to a system'in'wlilch a currentLof air is maintained at a preiieterrninetl pressure sc as to liiowfina'givenidirection and YAin particular vto Aa control systemembodyinga cheek valve and means fior closing @the same Ito'-i'aifeyent l son the blower may-stop oiaslovv' doWnfmateriaHy. Hence, there maybe a -fcomple'te failure v'of air pressure or such a l:drop therein Vin'tlie conduit as to -be insufcient 'to suppoiit fthe Acolalys't iii the tower, and as a result-'there will be4 a 'batik flow of the catalyst toward `the blower. When this happens the -blower becomes clogged with the catalyst Which-results zin loss' ofprouetion and damage tothe equipment. To prevent this, it has been fcustomary ito place a check valve in the conduit between thebloWer-dah the--eata lyst tower operable upon `reducticnlor ailuieo the air pressure toclose the conduit. Because (if the fact thatsuch valvesfnormally occupyuaiwide open position Jfor lo'n'g periods -o'f itime, :diie to infrequent operation, their bearings fbecoming dirty or rustyso that they stlckfandfdonotclose readily and quick enough to Vprevent `.dow fbaok. For this reason Lthere have been Iprovided waive actuating means -for )positively #closing the check valve, this means being connected in ato the oil pressure system of Ithe {turbinefso -thatii'f the'turi bine is shut down 'by the 4`Yoverspeed tripfor slows down due to -a `drop in -steam pressuret-he ivalve will automatically be closed by' -`the -aceomp'ar"1ying drop-infpressure nitheoi'ltpressureisystem.

Such a controlfsystem is sluggish anxiur'nfea liable in operation. qsince it iis' possible for the air pressure in the conduit to fall sufiiciently to permit'the catalyst to gradually creep Y.back `in the conduit by slowing down of the turbine without an accompanying drop in the oil.,- pressure which is suiiicient to actuatethe aforesaid valve actuating means; hence an object of this invention is to provideother sandfmoreireliable-means independent df the Eturbine 1v'(ilpiessure fior finitiating Iclosing movement "of :the 'valve :as -soonas the catalyst begins to creep baci: ito' 'fthelfioon duit. Y`

11i claims. (C1. ,ase-.21189 Accordingly, as illustrated herein, Athe iinvenitionzresdesfinaone aspectzinfa'systemrinawhichair pressure created :by a fblower iunit is employed :to maintain :a linely divided .solid matter 1in @suspension atza-.plaoerof suspension, thatfis a catalyst tower. in which a check valve is dsposeddn -a-'fconduit .between :the-blower -unit fand the tower, which lis ,free .to )movie l between a tclosed :and open position and which-isnormally held-open by the air lpressure :in fthe ,conduit cand .in which y.a Vdetector :such Jas a photoelectric 'device or the like means responsive rto l.the presence .of suspended particles yin the .air tstream, is .disposed xin .the conduit at the supstream v.side l.of `.the check valve, that is, between the check Valve and the catalyst tower, the `detectorfbeinglconnected withxa' relay or the like capable tof effecting the .actuation of the check valve .to .a .closed position .upon deterition-:of.thepresenceof solid partiolesin the conduit. 'Iheretis 'interposedbetweenlthevhek valve and the .detector 4an actuator .movable 'froi f an inoperative .toanoperative .position and .t eiect, by movement to Vits `operative position, operation oficheck-valvetoaclosed position. .Ihe actuator is held during noiiiloperatinrof the vsys- .temin an .inoperative position by liid 'pressure from the 'blower-driving Ymechaijusni and is only permitted torbecome Aoperative at'such times as the afesai ,phdtoe'lectic device, or the ilike means, :detects particles in Lthe conduit, whereupon a Valve a'issoiaei with tthe 'uid pressure system is operated to ventr z:relieve the pressure, athefvalve being normally held in alclosed position against springrmeans iby a latch :operatedfby'a :solenoid-or fthe 'like associated v:with fthe detector so as to :permit `:the -zvalve :to open fthe ventin 'response to operation o'f athe :detecten` EThefdetectorfpreterablyfcoxmznrisesy a;photoelec; tricmeans,.=suchasithe conventional :light-:sensitive' cell,l and "'li'ght source :mounted im diametrialiy vr.disposed iopenings L in .fthe wall ylof v:the foonduit. 'Each-element includes .a tube let tinto :the wallfoffthefconduit .and preerably'providednwith ahardeied Lglasslens laait its .exposed firmer :end substantially iflush vwit'h :the einher. surfaee fof 'the conduit to resist abrasion Aand pressure and 'to exclude' dii-rt '.there'iifom. lenses ,may the come:dirty ornfoggedlbyflust andzmoistui'e, and

hence aeect :improper :operation of fthe control system when there is no solid matter present :in the zconduit, :so athat at intervals itheyshouldabe cleaned. It *is another object Tof ethis .inuention tirez' eoreato'proiiideuireansforsnemovablymount ing tlzelements the 'phatoeleotrie :means in 'the Ltheaeondiiitf'so that 'ntheyzzmay ,cbe frethe conduit and means associated therewith for closing the apertures left by the elements when they are removed for cleaning purposes without reduction of the air pressure in the system. The aforesaid means comprise housings secured to the wall of the conduit over the apertures therein, the housings having bearing apertures aligned with the openings formed in the conduit for the reception. of the elements of Ythephotoelectric means and in which they are slidably disposed With their ends ush with the wall of the conduit, and a valve member rotatably mounted within each housing operable when an element is withdrawn from the housings to close the associated bearing aperture.

f The invention will now be described'in -detail with reference to the accompanying drawings which illustrate what is now considered a preferred embodiment of the invention. In the drawings:

Fig. 1 is a diagrammatic layout of a pressure system in Which there are pressure creating means, a conduit for conducting air under pressure from the pressure creating means to a catalyst tower and valve means in the conduit for preventing back flow of catalyst in the system;

Fig. 2 is a section on the line 2-2 of Fig. 1 showing the mounting for the photoelectric elements;

Fig.` 3 `is 'a rsection on the line 3--3 of Fig. 1 showing the valve closing means; Y

Fig.,4 isa section on the line 4--4 of Fig. 3 showing the closure valve in a closed position;

Fig. 5 is a section through a pilot valve, the position of which is controlled by reduction of the oil pressure in the turbine oil pressure system;

' Fig. 6 is a section through a pilot valve, the position of which is controlled bythe presence of solid matter in the conduit;

Fig. 7 is an elevation, partly in section, on the line 1-1 of Fig. 6;

Fig. 8 is a transverse section through one of the housings for removably attaching the photoelectric elements to the wall of the conduit, showing an element in position; and

Fig. 9 is a similar section showing the element removed and the valve closed.

Referring to Fig. 1 the system is illustrated as comprising a conduit I0 which is connected at one end to ablower or fan I2 and leads therefrom to a catalyst tower a fragmentary portion of which is shown at the right-hand side of Fig. 1. The. blower I2 is driven by a turbine I4 which is supplied with steam from a pressure line I6. Interposed in the conduit I0 between the fan I2 and the catalyst tower is a check valve housing I8 which, as shown in Figs. 3 and 4, contains a check valve 20. The check valve 28 has fixed thereto an arm 22 having integral with an end thereof a sleeve 24 (Fig. 3) which is mounted for free rotation on a shaft 26 so that thecheck valve is free to swing between open and closed positions.

In order that the check valve may positively be moved toward a closed position, however, one end of the sleeve 24 has diametrically disposed recesses 28 cut therein with which cooperate diametrically disposed shoulders 3D formed on a bearing member 34 which is one of a pair of bearing members 32 and 34, in which the ends of the shaft rest and which support the shaft between the walls of the housing I8. By rotation of the bearing member 34 in a clockwise direction as seen in Fig. 4, one of the shoulders 30 may be brought into engagement with a forward Wall at one end of the recess" 28 which it occupies to apply a force to the check valve to close it and to hold it in a closed position. The bearing member 34, however, is normally held in an inoperative position, as shown in Fig. 4, wherein the Vshoulders 30 occupy a substantially horizontal position and when so held, because of the width of the notches 28it is evident that the check valve is free to swing between a closed and an open position without interference.

Rotation of the bearing member 34 is eiected as follows: Extending laterally from the bearing member 34 is a shaft 36 which, as shown in Fig. l, is connected by an arm 38 to the upper end of apiston rodr 40. The piston rod 4I! passes through an end Wall of a cylinder 42, a suitable gland 44 being provided for this purpose and has fixed to its lower end a piston 46. There is disposed between the upper closed end of the cylinder and the piston, surrounding the rod 48, a compression spring 48 which normally urges the piston toward the bottom of the cylinder and when urged in this direction urges the arm 38 in a clockwise direction as seen in Fig. 1, which in turn rotates the bearing member 34 in a clockwise direction so as to close the check valve 20 vas hereinbefore pointed out.

The spring 48 however is normally held inactive by iiuid pressure which is delivered to the underside of the piston 46 at the lower end of the cylinder 42 by oil delivered thereto under pressure through a conduit 50 which, as shown in Fig. l, is connected into the oil pressure system of the turbine I4. As long as the oil pressure in the turbine oil pressure system remains normal the pressure against the underside of the piston 46 Will be* sufficient to oppose the force of the spring 48. If, however, through any reason the oil pressure in the turbine oil pressure system drops by reason of a reduction in speed of the turbine, for one reason or another, or of a shutting down of the system, the oil pressure below the piston 46 will be vented as will appear hereinafter and the spring 48 will force the piston 46 downwardly and hence move the check valve to a closed position.

k It is to be observed that While the spring 48 is strong enough to move the check valve to a closed position, that is, to overcome any sticking of the valve on the shaft it is light enough so that its full force is insufficient to hold the check valveA p. s. i. 16,"valve 1.80 18 valve 1.29 20" valve .95 24" valve .57

Hence, if the check valve-is accidentally closed,

it is not held in a'closed position with sufficient pressure to shut down operation of the system.

A fall in pressure in the turbine oil pressure system is caused to by-pass, that is vent the oil 5. in `the .lower `portieri .of the :cylmder M through a -passage v52 .leading "therefrom to a ipassage 54 formed lin .a pilot :valve 'housing 56 (Fig. "51). the pilot valve vhousing and cylinder being secured together .with the .passages 52. zand .251| .in registration .by suitable .flanges surrounding the same. The pilot valve `housing 56 V'has init afslide valve 58, Vthe .lower `end 60 of which -is adapted to enf gage a valve seat 62 at vthe inner 'end 'of a passage 6d opening into ya chamber :Within the valve housing with which the :passa-ge xt 'communi- Cates. As shown in Fig. .1 the outer end `of lthe passage 64 ris connected kto a short -leader `66, `the latter being connected .to areturn duct -68 which carries the oil back to an oil reservoir 1.0 .of the turbine. The Valve .518 is .normally .held against its seat 'by oil pressure fin .the turbine .oil lpressure system conducted .thereto 'through a conduit l2 which enters .the upper ,portion of the Valve housing at '14 .and -acts on the upper 4surface of an enlarged head 'T6 -formedin'tegr'al with the pilot valve 58. 'When the vpressure in the turbine oil pressure system falls, however, a spring i8, disposed around vthe slide Vvalve "between the head 16 and llateral 'shoulders v`8l) formed internally of thehousingymovesithe slide valve upwardly to lift its 'end 60 Yfrom the seat 62 so as to permit oil "from the lowerpart'of the cylinder t2 to pass from it into'thevalvehousingT 53 'and 'out through the passage '64.

lAlthough the aforesaid means will provide 'for closing of `the check valve uponshutting'down of the turbine or upon material vfreductionvoi the speed thereof, this "invention ehowever contemplates the use of additional and more sensitive means for closing the valve 20 'which ldepends solely `upon the presence of solid matter in the conduit indicative of ow backyand as `illustrated herein comprises photoelectric means vadapted when actuated to vent ythe oil `pressure in the cylinder :i2 in a manner somewhat similar to that just described. Accordingly, and as illustrated in Fig. 6, there Iis bolted to the `opposite side of the cylinder 542 by means of lsuitable anges a valve casting 584 (Fig. 6) lhaving .a lateral passage 82 therein.leading to la "central longitudinal chamber 90 within which 'there Vis disposed a slide valve 86. The slide valve v855.-has a lower end E0 arranged closely to fengage the chamber Sil and to .cover the .lateral :passage 84 leading into it. 'The lower end 'o'f the chamber is open and a iiange92 formed on the 'valve casting surrounding the same provides means for bolting Athereto the flanged end -94 of the fconduit E3 (Fig. l) so that movement vof the :slide valve Se in the chamber 90 lto uncover the .passage 82 will permit venting ofthe oil from the cylinder 42 to the return duct 68 -of the turbine oil reservoir. The slide valve 8| isconnected to the lower end of a valve'rod 94 which has xed to its upper end a'cap 96 arranged to slide telescopically in an enlarged recess A'lltformed -in a hollow post iixed to the top-of Ithe valve-'casting and between which and 'thebottom of .therecess there is disposed aspring |00. The Valve .stem S4 has an annular shoulder |02 formed thereon by turning itfdown in diameter, and this annular shoulder is adapted 4to be engaged -.byf.-ashoulder I0@ formed on a shaft 406, bycutting a slot |08 halfway throughit fromside -to side. The=shaft |06 is journaled at its `opposite ends .in bearings |10 formed laterally of the lpost and has .fixed toene end an arm |.2 (Fig. 6) which is arranged to .be yheld yin engagementl with one -end of .a plunger i4 .of a solenoid |.|I6, the llatterbeing fixed `to 1.a bracket extending .laterally ironi'zthe casting. .A :spring :H8 (Fig. 17.), fsurroumlmg .ta reduced portion 'of the shaft |06 :andseated'fa recess .|22 :formed iin one "of the bearings, :ser-ves yieldably .to .hold .the arm .H2 :in vcontact 'with the `plunger v| lil. .'In -.the yull line 'position shown in Fig. 6 thefshoulder |04 in :enga-'gement with' the annular shoulder :I0-2 "and thus holds the valve B6 :inia closed position in vopposition to the sprlin'g .106. Upon excitation fof the solenoid 1| |16 however, zthe .farm .H2 is .moved to .the .dotted lline position, "thereby withdrawing the shoulder 404 from the shoulder |02 so .that the ispring :|100 raises the yalyerod 3'4 and hencezopens ithe valve 8| Lto permit venting-oi `:the'oil .-from beneath the piston $6. .The slide valve may -beclosedraiter thefcon'ditien in the system has been remedied by manually pressing the cap 96 so as to reengage the shoulder A|02 v'with the shoulder '104.

'The 'solenoid H6 is excited 'byphotoe'lectric means '|22 (Fig.` '11) to which it Pis-connected by way of y'a relay |211, suitable electric connections |26 .being provided :for connecting the iphotoelectric .'means, vrelay and solenoid to an :outside source of electric power. The Vphotoelectric means l22consistsof theusual light sensitivefcell and light source and are vmounted lindiametrically opposed openings |28 (Figs. Sand 49) lin the wall of the vconduit 10. As thus lmounted the elements may be adjusted as .to sensitivity so that the presence 'of a small amountof-solidmaterial in .the conduit which would befindicativefof counterflow in the `conduit will cut foiivsunicient light from the light source to cause the light sensitive cell to vfunction in a manner to actuate the relay.

In order that these photoelectricelements may readily be mounted and removed for cleaning purposes without reduction in thepressur'eof Athe system and so that lthe system need not be shut down whilesuch-cleaning is taking placegthe-el'ements are provided with a special mounting means which are illustrated in Figs. 8 .and 9. As shown therein yoke-like plates |24 'are Welded to the opposite sides of the conduit 'H0 and'have in .them apertures |26 which are concentric'with the 4openings Av|28 inthe conduit l0. .A housing |30, having a chamber |32 therein, fa .neck |34 at one end and a neck |36 at the otherend and formed with a vflange |38 adjacent to Athe `neck |34, is secured toeach yoke |24 by-bolts |40 so that Vthe neck |34 extends through -the concentric apertures |26 and |28. .Each housing |30 has internally'of its neck I.portions 'bearing-openings |42 and |44 (Fig. 8') which arealso concentric with the apertures |26 and |28 .forslidably receiving a tube |46 (Fig. 8*) which has at its inner end a'lens |48 which occupies aposition which is substantially llush `with the inner surface of the conduit l0. The tube Id@ forms an extension of a shorter .tube |50 Vprojecting laterally from the lightsensitive elementor the light source as the case `may be and `with which it is telescopically engaged. .A flange .|.5| .on the outer `end of the tube |46 provides meansiorfsecuring it and .hence the particular elementto .the housing, .and for this purposelbolts'l53 are. shown as passing through the 4flange |5| .and being threaded at their inner .endsinto the `flange |38. Within the chamber |32 and surrounding .the outer one of the bearing openings l|l2 there iis an inclined annular valve seat |54 .against `which there is adapted to be seated a valve member |56, the latter being fastened toa shaft '|58 which is journaled v.in 'the .walls of 'the 'housing 'above lthe opening and has on one end a lever |60 by means, of which it may be swung into an open position to admit the tube |46. The valve will fall by gravity automatically as the light sensitive element or lightl source when withdrawn together with the tube |46, to close against the seat |54, the closed position of the valve being illustrated in Fig. 9. A cover plate |62, positioned at the top of the housing |30 and bolted thereto, provides means for covering the access opening |63 formed therein and through which the condition of the valve and its seat may be examined. A transparent cover plate |64 (Fig. 1) is also provided in the conduit I at the top thereof above the photoelectric means through which the condition of the plate glass lenses |48 may be observed without removing the elements from their housings.

There is also provided in the system a densometer |66 (Fig. 1) which is suitably electrically connected into the electric connections for the photoelectric means to indicate the density of concentration of particles in the conduit at any given time, the densometer being sensitive enough so that it will register on a dial the presence of particles in the conduit which are not sufficient in concentration to operate the photoelectric means. Preferably a signal in the nature of a red light may be operated by the densometer to indicate that there is an appreciable concentration of particles in the conduit.

In operation, assuming that the blower is developing sufcient pressure to hold the catalyst in suspension in the catalyst tower, the check valve 20 will occupy its wide open position, the .r

piston actuated mechanism for closing it being held in an inoperative position by the oil pressure below the piston 4S. If now for some reason particles of the catalyst begin to creep back into the conduit, they actuate the photoelectric means f |22 in the conduit which, through the relay |24, solenoid ||6, latch ||2, and valve 88, vents the oil from below the piston 46 thereby bringing about closing of the check valve 20, irrespective of whether there has been a drop in pressure in the system of sucient magnitude to bring about closing of the check valve through the pressure actuated valve 58.

I claim:

1. Apparatus for use in effecting catalytic reactions comprising a reaction tower in which a` quantity of fine particles of solid catalyst are to be air-borne in suspension a blower and a conduit connected at one end to the blower and at the other end to the tower through which a current of air under pressure is delivered near the bottom of the tower by the blower of suflicient intensity to hold the major portion of the catalytic particles in suspension in the tower and, means for preventing gravitating particles from returning through the conduit to the blower, said last means comprising a check valve in said conduit between the tower and the blower, said check valve being free to move between open and closed positions and being normally held open by said air pressure in the apparatus, and means in the conduit between the valve and tower `for initiating actuation of said valve to close the same in response to the presence of traces of solid matter in the air stream.

2. Apparatus for use in eiiecting catalytic reaction comprising a reaction tower in which a quantity of solid particles of catalyst are to be air-borne in suspension a blower and a conduit connected at one end to the blower and at the otherend to the tower through which a current of air under pressure is delivered near the bottom of the tower by the blower of sufficient intensity to hold the major portion of the particles of catalyst in suspension in the tower and, means for preventing gravitating particles from returning through the conduit to the blower, said last means comprising a check valve in said conduit between the tower and blower, said check valve being free to move between open and closed positions and being normally held open by said air pressure, means connected to the valve operable to close the same and means in the conduit between the valve and tower responsive to traces of solid matter in the air stream for actuating said last named means to close the valve.

3. Apparatus for use in eiecting catalytic reactions comprising a reaction tower in which a quantity of ne particles of solid catalyst are to be air-borne in suspension, a blower, and a conduit connected at one end to the blower and at its other end to the lower part of the tower through which a current of air under pressure is delivered to said tower by the blower of suficient intensity to hold the major portion of the catalytic particles inV suspension in the tower, and a check valve in said conduit between the blower and said tower operable to close said conduit, said check valve being free to move between a closed and an open position and being normally held open kby the air pressure in the conduit, means movable from an inoperative to an operative position to close said check valve, a spring pressed piston connected to said rst named means normally urging it toward its operative position, means for holding said spring pressed piston inoperative and photoelectric means in the pressure conduit between the check valve and the tower, operable by the presence of particles in said conduit to render said spring pressed piston operative.

4. Apparatus for use in effecting catalytic reactions comprising a reaction tower in which a quantity of ne particles of solid catalyst are to be air-borne in suspension, a blower, and a conduit connected at one end to the blower and at its other end to the lower part of the tower through which a current of air under pressure is delivered to said tower by the blower of sufficient intensity to hold the major portion of the catalytic particles in suspension in the tower, a check valve in said conduit between the blower unit and said tower operable to close said conduit, said check valve being hinged to move between a closed and an open position and being normally held open by the air pressure in the conduit, means movable from an inoperative to an operative position to close said check valve, a spring pressed piston connected to said rstmeans normally urging it to its operative position, a source of iiuid pressure in communication with said piston opposing operation of said spring, and photoelectric means in the pressure conduit between the check valve and the tower operable by the presence of particles in said conduit to vent the iluid from said source of fluid pressure.

5. Apparatus for use in effecting catalytic reactions comprising a reaction tower in which a quantity of ne particles of solid catalyst are to be air-borne in suspension, a blower, and a conduit connected at one end to the blower and at its other end to the lower part of the tower through which a current of air under pressure is delivered to said tower by the blower of sufficient intensity to hold. themajor,` portion of the catalytic particles in suspensionin thel tower, a check valve in said conduit between theblowerunit and said tower. operable to. close said conduit, said check valv'ebeing hinged to move'between a closed and an. open position and being normallyheld openiby the air pressure inthe conduit, means movable from an inoperative to an operative position to close said check valve, a piston connected to said first means, a spring constantly urging said -piston in a direction to move the rst means to its operative position, a source of fluid pressure in communication with the opposite side of said piston holding the spring inoperative, a valve for venting the fluid from behind said piston, and photoelectric means in the pressure conduit between said check valve and the tower operable to cause said valve to vent said fluid pressure.

6. Apparatus for use in effecting catalytic reactions comprising a reaction tower in which a quantity of fine particles of solid catalyst are to be air-borne in suspension, a blower, and a conduit connected at one end to the blower and at its other end to the lower part of the tower through which a current of air under pressure is delivered to said tower by the blower of sufcient intensity to hold the major portion of the catalytic particles in suspension in the tower, a check valve in said conduit between the blower unit and said place of particle suspension operable to close said conduit, said check valve being hinged to move between a closed and an open position and being normally held open by the air pressure in the conduit, means movable from an inoperative to an operative position to close said check valve, a spring-pressed piston yieldably urging the rst means to an operative position, a source of fluid pressure in communication with the piston holding it in an inoperative position against said spring, a by-pass forV bleeding fluid from said source of fluid pressure, a valve movable from a -position blocking said by-pass to a position uncovering it, a spring normally urging said valve to an uncovering position, ar

latch holding said valve in a blocking position, and photoelectric means in said conduit between the check valve and tower operable by the presence of particles in the conduit to release said latch.

7. Apparatus for use in eiecting catalytic reactions comprising a reaction tower in which a quantity of fine particles of solid catalyst are to be air-borne in suspension, a blower, and a conduit connected at one end to the blower and at its other end to the lower part of the tower through which a current of air under pressure is delivered to said tower by the blower of suincient intensity to hold the major portion of the catalytic particles in suspension in the tower, a shaft in said conduit, a check valve, an arm fixed at one end to said check valve and having a sleeve at its opposite end surrounding said shaft whereby said check valve is hinged to swing between open and closed positions in the conduit, said check valve being normally open, a member surrounding said shaft adjacent to one end of said sleeve, said end of the sleeve having a notch therein and said member having a shoulder projecting into the notch, means operable to rotate said member relative to the sleeve to cause said shoulder to engage an end of the notch to move the check valve to a closed position and photoelectric means between the valve and the tower operable by the presence of air-borne pari ticles in theI conduitv to eff-ect operation of said last-named means.

8. Apparatus. for use in electing catalytic reactions comprising. a reactiontower in which a quantity of fine particles ofi solid, catalyst are to be air-borne in suspension, a blower, anda conduit connected atv one end to the blower and at its other endk to the lower part of. the tower through whicha currentot air under pressure is delivered. to saidztower. bythe blower ofsufficient intensity to hold the major portion of the catalyticparticlesiin suspension in the tower, a check valve in said conduit between the blower unit and said place of particle suspension operable to close said conduit, said check valve being free to move between a closed and an open position and being normally held open by the air pressure in the conduit, spring-pressed means urging the first means to an operative position, said springpressed means being held inoperative, and photoelectric means in said conduit between the valve and tower operable by the presence of particles in the conduit to release said spring-pressed means, said spring-pressed means being ineffective to hold said valve in a closed position against normal air pressure in the conduit.

9. In an apparatus including a blower unit, a catalyst chamber and a conduit extending between the two through which air under pressure is delivered from the blower to the lower end of the catalyst chamber for holding a nely divided catalyst in suspension therein, a valve interposed in the conduit which is adapted to be closed by a photcelectric means disposed between the valve and the catalyst chamber and photoelectric means, said conduit having apertures in its peripheral wall for the reception of said photoelectric means, means for removably supporting the photoelectric means in said apertures of the conduit, and means for automatically closing the apertures left by the photoelectric means when the latter is removed to maintain the pressure in the system.

10. In an apparatus including a blower unit, a catalyst chamber and a conduit extending between the two through which air under pressure is delivered from the blower to the lower end of the catalyst chamber for holding a nely divided catalyst in suspension therein, a valve interposed in the conduit which is adapted to be closed by a photoelectric means disposed between the valve and the catalyst chamber and photoelectric means, said conduit having apertures in its peripheral wall for the reception of said photoelectric means, a housing bolted to the wall of the conduit over each aperture, each housing having a bearing opening therein concentric with said aperture for the reception of an element of said photoelectric means removably to hold it flush with the inner wall of the conduit, and a valve in said housing automatically operable upon withdrawal of an element to close said opening.

11. In an apparatus including a blower unit, a catalyst chamber and a conduit extending between the two through which air under pressure is delivered from the blower to the lower end of the catalyst chamber for holding a nely divided catalyst in suspension therein, a valve interposed in the conduit which is adapted to be closed by a photoelectric means disposed between the valve and the catalyst chamber and photoelectric means, said conduit having apertures in its Iperipheral wall for the reception of said photo- 2,599,197 11 12 electric means, a housing bolted to the Wall 0f Y REFERENCES CITED the conduit over each aperture each housing The following references are of record in the having spaced bearing openings therein concenme of this patent:

trio with said aperture in the conduit in which an element of the photoelectric means is disposed 5 UNITED STATES PATENTS with its inner end ush with the inner surface Number Name Date of the conduit, the outer one of the bearing open- 2,311,374 Farmer et al Feb. 16, 1943 ings having a surrounding Valve seat and a valve rotatably mounted in each housing gravitationally operated upon withdrawal of an element from 10 the housing to engage said seat.

NORMAN F. PRESCOTT. 

